Pump

ABSTRACT

In a pump having a rotor inside a pump chamber which is formed inside a case which is formed of a resin material, and a resin mold compound in which an armature is molded with resin, a metallic cover is provided on a portion of an outer surface of the case inside the pump, wherein the portion has inferior durability compared with the rest of the outer surface.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to pumps, and more particularly to a pumphaving improved hydraulic pressure resistance by increasing thedurability of the exterior and interior of the pump, having therein acase formed of a resin material.

2. Description of the Related Art

There is a growing demand for a device such as a water heater to becomesmaller in dimensions, lighter in weight and energy efficient. Suchdemand is also expected of a pump installed in the aforementioned deviceor the like.

A pump in general comprises a DC brushless motor having a rotor which issealed inside a case, a stator affixed outside the case for driving therotor, and an impeller which is connected to the rotor and is located ina pump chamber therein.

FIG. 8 is a diagram showing a schematic cross sectional view in an axialdirection of an example of a conventional pump. As shown in FIG. 8, apump 100 has arranged therein a rotor 121 in an interspace between anupper case 111 and a lower case 112 which are formed of a resinmaterial. The pump 100 also includes an annular shaped stator 122 alongan outer circumferential surface of the rotor 121. A pump having suchconfiguration is commonly referred to as a canned type pump.

The upper case 111 and the lower case 112 sandwich an O-shaped ring(hereinafter, referred to as an O-ring) 115, and seal an inner portionof the pump 100. Also, a pump chamber 116 is provided at an upperportion of the interspace. An intake portion 113 and a discharge portion117, which are connected to each other in the pump chamber for,respectively, intaking and discharging fluid, protrude outwardly fromthe upper case 111. The aforementioned configuration is to be formedintegrally.

The rotor 121 is supported and allowed to freely rotate in a radialdirection by a cylinder shaped sleeve 125 located surrounding a fixedshaft 123 which is affixed at a center of the pump 100 inside the lowercase 112. Also, a thrust washer 124 is provided at top and bottomportions of the sleeve 125 so as to support in the axial direction andallow the rotor to freely rotate.

The rotor 121 comprises an impeller base portion 126 which is connectedto the sleeve 125, an impeller 127 which is affixed above the impellerbase portion 126, and a rotor magnet 128 which is surroundingly affixedto the rotor 121. The rotor magnet 128 is provided within a cup shapedportion 112 a in the lower case 112.

The stator 122 comprises an annular shaped resin mold compound 133including therein a molded resin 132 in which a printed circuit board131 and an armature 134 which includes therein an annular shapedlaminated core 129 and a coil 130 are provided.

The resin mold compound 133 is located on an outer circumferentialsurface of the rotor magnet 128 of the rotor 121 and is affixed to thelower case 112. The resin mold compound 133 and the rotor 121 configurethe DC brushless motor. When an electric current is applied to thestator 122 via the printed circuit board 131 from an external powersupply (not shown in the figures), the impeller 127 rotates along withthe rotor 121. Due to the rotation of the impeller 127, fluid is takenin through the intake portion 113 to the pump chamber 116. Then, thefluid pressured by the impeller 127 will be discharged from thedischarge portion 117.

For the aforementioned pump 100, metallic cases having a superiordurability than the resin based upper case 111 and the lower case 112are used so as to sustain expansion, which is caused by the hydraulicpressure, of the resin based upper case 111 and the lower case 112, andto improve hydraulic pressure resistance of the pump 100.

However, forming a metal plate into a three-dimensional case by methodssuch as pressing and welding will be a difficult task. Further, thepressing process is a costly process. Furthermore, such pump requirescountermeasures against increased weight thereof and corrosion.

Also, according to the pump 100 as shown in FIG. 8, at a contact portion136 where the lower case 112 and the annular shaped resin mold compound133 make contact with each other, the resin mold compound 133 will beaffected, via the lower case 112, by the pressure which is generatedwithin the pump. When the pressure within the pump is increased, due tothin resin layers at the contact portion 136, the resin mold compound133 may be damaged (e.g., occurrences of crack). Ultimately, if thepressure continues, the resin mold compound 133 may be detached from thelower case 112.

Also, in the pump 100, a gap S may be generated between an innercircumferential surface of the resin mold compound 133 affixed to thelower case 112 and an outer circumferential surface of the lower case112. Each time the case 112 is affected by the pressure from the pump,the gap S may be repeatedly widened. Then, a weld line having a weakconnection is likely to be cracked and, thus, water leakage of the pump100 may occur.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a pump having a structure in which ametallic cover is attached to a case, which is formed of a resinmaterial, so as to increase the durability of the pump having thereinthe case. Also, the present invention relates to the pump having astructure in which a reinforcement board is provided to the case so asto increase the durability of the case inside the pump. The presentinvention improves, without any significant increase in weight and aproduction cost thereof, hydraulic pressure resistance of the pumpthereby increasing the durability of the pump.

Further, since the metallic cover is attached to a resin mold compoundhaving molded therein an armature, the durability of the resin moldcompound will be increased.

Furthermore, the metallic cover can be embedded in either the case orthe resin mold compound.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram showing a schematic cross sectional view, in anaxial direction, of a pump according to a first embodiment of thepresent invention.

FIG. 2 is a diagram showing a plan view of the pump shown in FIG. 1 asseen from a side of a fluid intake portion.

FIG. 3 is a diagram showing a plan view, as seen from a side of, a pumpaccording to a second embodiment of the present invention.

FIG. 4 is a diagram showing a schematic cross sectional view, in theaxial direction, of a pump according to a third embodiment of thepresent invention.

FIG. 5 is an enlarged view of a portion A shown in FIG. 4.

FIG. 6 is a diagram showing a schematic cross sectional view, in theaxial direction, of a pump according to a fourth embodiment of thepresent invention.

FIG. 7 is an enlarged view of a portion B shown in FIG. 6.

FIG. 8 a diagram showing a schematic cross sectional view, in the axialdirection, of an embodiment of a conventional pump.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of a pump according to the present inventionwill be described with reference to FIGS.

First Embodiment

FIG. 1 is a diagram showing a schematic cross sectional view in an axialdirection of a pump 10 according to a first embodiment of the presentinvention. FIG. 2 is a plan view of FIG. 1. As shown in FIG. 1, the pump10 comprises: an upper case 11 and a lower case 12, which are formed ofa resin material; a rotor 21 which rotates around a predeterminedcentral axis J1, and which is located in a space generated between theupper case 11 and the lower case 12 which are joined together; and aring shaped stator 22 which is located along an outer circumference ofthe rotor 21 and outside of the lower case 12. The pump 10 is commonlyreferred to as a canned type pump wherein the lower case 12 is providedbetween the rotor 21 and the stator 22. Note that, in the description ofthe preferred embodiments of the present invention herein, words such asupper, lower, left, right, upward, downward, top, and bottom fordescribing positional relationships between respective members anddirections merely indicate positional relationships and directions inthe drawings. Such words do not indicate positional relationships anddirections of the members mounted in an actual device.

The upper case 11 and the lower case 12 sandwich an O-ring 15, and sealan inner portion of the pump 10. At an upper portion of an interspaceportion generated by the upper case 11 and the lower case 12, a pumpchamber 16 is provided. An intake portion 13 and a discharge portion 17which are connected to each other in the pump chamber 16 protrudeoutwardly from the upper case 11. The aforementioned configuration is tobe formed integrally.

The rotor 21, sharing the same axis as the central axis J1, is supportedand allowed to freely rotate, via a sleeve 25 and a thrust washer 24located at both top and bottom of the sleeve 25, by a stator shaft 23fixed between the upper and lower cases 11 and 12.

The rotor 21 comprises: an impeller ba1se portion 26 which is connectedto the sleeve 25 formed of the resin material (e.g., polyphenylenesulfide) having a tribological property; an impeller 27 which isconnected to a top portion of the impeller base portion 26; and a rotormagnet 28 which is located surrounding the sleeve 25. The rotor magnet28 is located inside a cup shaped area provided in a center portion ofthe lower case 12.

The stator 22 comprises: an armature 30 including therein an annularshaped laminated core 29 and a coil 29 a; and a printed circuit board31. The printed circuit board 31 and the armature 30 are molded in amolded resin 32 configuring an annular shaped resin mold compound 33.

The resin mold compound 33 is located on an outer surface of the lowercase 12 which is located along an outer circumferential surface of therotor magnet 28 in the rotor 21. The resin mold compound 33 is affixedto, so as to cover, an outer circumferential surface and a portion of abottom of the cup shaped lower case 12. Further, the resin mold compound33 extends radially outwardly from the cup shaped lower case 12 isaffixed to, so as to cover, an outer surface forming the pump chamber16. Since the outer surface of the lower case 12 and the resin moldcompound 33 make contact with each other as described above, the resinmold compound 33 is able to sustain expansion of the lower case 12 evenif the pressure within the lower case 12 is increased.

The motor according to the present invention is a component of thebrushless DC motor such that when the stator 22 is supplied with anelectric current from the printed circuit board 31, a rotating magneticfield will be generated in the stator 22, thereby rotating the rotor 21.When the rotor 21 rotates, the impeller 27 connected to the rotor 21rotates. Then the fluid will be sucked in to the inner portion of thepump chamber 16 through the intake portion 13, directed by the impeller27 to flow in a predetermined direction, and discharged through thedischarge portion 17.

In the pump 10 according to the present embodiment, an annular shapedmetallic cover 1 is provided covering over an outer surface of the uppercase 11. The metallic cover 11 is secured by a screw 2 at four points tothe upper case 11. Here, the screws 2 each are to be used at pointsavoiding the pump chamber 16 so as to avoid exposing the screws 2 to theinner portion of the pump chamber 16. If the screws 2 are exposed to theinner portion of the pump chamber 16, the fluid inside the inner portionmay leak outside thereof. Also, if screws 2 not long enough to penetratethe metallic cover 1 are used, the metallic cover 1 will not be securedto the upper case 11. Also, providing a layer having an increasedthickness for the upper case 11 so that long screws 2 can be used, thedimensions of the pump 10 will be large. In order to solve theaforementioned problems, the screws 2 are provided ideally at pointsavoiding the pump chamber 16.

In general, in a pump, which has a case formed of a resin material,whose rated total head is approximately 13 m or smaller, and whose ratedflow is approximately 30 L/min or smaller, a maximum internal pressureof fluid a pump chamber can withstand is between, approximately, 200 KPato 250 KPa. When the internal pressure is to be greater than 250 KPa, ametallic case will be necessary in order to sustain the expansion.However, when the upper case 11, which is formed of the resin material,has applied thereon the metallic cover 1 in the pump 10 according to thepresent embodiment, an internal pressure up to approximately 1000 KPacan be withstood. Therefore, the pump 10 can be used for a pump in whichthe internal pressure of the fluid in a pump chamber exceedsapproximately 250 KPa.

The metallic cover 1 provides an opening 3 for insertion of the intakeportion 13 which protrudes from the upper case 11. Also, the metalliccover 1 can be easily manufactured by pressing a stainless steel plateor an aluminum base plate. Also, the metallic cover 1 can be attached tothe pump 10 easily. Also, the metallic cover 1 is attached, to the uppercase 11, stretching over a weld line (not shown in the figures) which isgenerated when the upper case 11 is formed by a die. Since the uppercase 11 is most vulnerable at the weld line, when the metallic cover 1is affixed covering over the weld line on the upper case 11, damages(e.g., occurrence of crack or expansion) can be prevented.

The metallic cover 1 is to be secured by the screw 2 at, at least, onepoint on both sides of the weld line. By this, the metallic cover 1 willbe able to prevent damages from being done to the weld line even whenthe internal pressure within the pump chamber 16 increases.

The metallic cover 1 increases the durability of the pump 10 havingtherein the upper case 11 and the lower case 12, which are formed of theresin material, to an extent of the durability of a pump having thereina metallic case. Further, the metallic cover 1 can easily bemanufactured and attached to the cases while keeping a weight increaseof the pump 10 to a minimum. Further, the metallic cover 1 can increasethe durability of upper case 11 which is repeatedly pressured by theinternal pressure of the fluid inside the pump chamber 16. As a result,a pump having the metallic cover 1 will last long and have an increaseddurability.

Further, a metallic cover different from the metallic cover 1 can beprovided on a surface, of the lower case 12, making contact with thearmature 30 in the axial direction. Note that thenon-metallic-cover-1-metallic-cover provides an opening for insertion ofthe cup shaped lower case 12. By this, the lower case 12 can besandwiched from both sides thereof in the axial direction, therebyconstrictedly securing the pump chamber 16. By this, the durability ofthe pump 10 against the internal pressure of the fluid within the pumpchamber 16 will be increased.

Second Embodiment

Next, a pump according to a second embodiment of the present inventionwill be described with reference to FIG. 3. FIG. 3 is a diagram showinga plan view, as seen from a side of, a pump according to a secondembodiment of the present invention. In FIG. 3, elements similar tothose illustrated in FIG. 1 are denoted by similar reference numerals,and description thereof is omitted.

In the first embodiment, the metallic cover 1 covers over only the topsurface in the axial direction of the upper case 11. In the secondembodiment, however, a metallic cover is provided on both top and bottomsurfaces of a pump 70 so as to sandwich, and to provide additionaldurability, to the pump 70. That is, according to FIG. 3, a metalliccover 71 which covers over a top surface of the upper case 11 and aresin mold compound side metallic cover 72 which covers over a bottomsurface of the resin mold compound 33 are provided on the upper case 11.The metallic cover 71 and the resin mold compound side metallic cover 72each are secured to the upper case 11 at four points by a screw 73. Acylinder shaped collar 78 is provided between the resin mold compoundside metallic cover 72 and the resin mold compound 33. The resin moldcompound side metallic cover 72 and the resin mold compound 33 each havepredetermined points (not shown in the figures) for the screw 73. Also,the upper case 11 and the metallic cover 71 each have predeterminedpoints (not shown in the figures) for the screw 73. Since the metalliccover 71 and the resin mold compound side metallic cover 72 areprovided, the durability of the upper case 11 and the resin moldcompound 33 will be increased. In particular, the resin mold compoundside metallic cover 72 affixed to the resin mold compound 33 increasesthe durability of the resin mold compound 33 so as for the resin moldcompound 33 to withstand greater internal pressure of fluid within thepump chamber 16 than the resin mold compound 33 without the resin moldcompound side metallic cover 72.

Note that, a planar shape of the metallic cover 71 and that of the resinmold compound side metallic cover 72 may be adjusted (e.g., round shape,substantially rectangle, or square) in accordance with a configurationof the pump.

Also, the metallic cover 71 and the resin mold compound side metalliccover 72 are affixed to a pump base 80 by a plurality of screws 82. Thepump base 80 is used to mount the pump 70 onto an apparatus. The pumpbase 80 has an extension portion 81, which extends toward the metalliccover 71 and toward the resin mold compound side metallic cover 72. Aportion of the extension portion 81 overlaps with a portion of themetallic cover 72 and with a portion of the resin mold compound sidemetallic cover 72. At the portions where the extension portion 81 andmetallic cover 72 overlap one another, and where the extension portion81 and the resin mold compound side metallic cover 72 overlap oneanother, openings 83 for insertion of the screws 82 are provided. Thepump base 80 is formed by pressing a metal plate. That is, the pump base80 can be manufactured inexpensively.

Since a primary object of the pump base 80 is to facilitate theconnection between the pump 70 and the apparatus (not shown in thefigures) onto which the pump 70 is to be mounted, the metallic cover 71and the resin mold compound side metallic cover 72 are not designed towithstand a great amount of pressure. However, the metallic cover 71 andthe resin mold compound side metallic cover 72 need to sustain expansionwhich may occur to the upper case 11 and the resin mold compound 33, andtherefore durability thereof against the pressure need to be increased.Thus, the metallic cover 71 and the resin mold compound side metalliccover 72 are designed to be thicker than a thickness of the plateforming the pump base 80. The thickness of the metallic cover 71 andthat of the resin mold compound side metallic cover 72 each are,preferably, greater than, approximately, 2 mm. When the thickness of themetallic cover 71 and that of the resin mold compound side metalliccover 72 each are greater than approximately 2 mm, the metallic cover 71and the resin mold compound side metallic cover 72 can sustain anexpansion, of the uppercase 11 and the resin mold compound 33, caused bythe internal pressure within the pump chamber 16. When the metalliccover 71 and the resin mold compound side metallic cover 72 each havinga thickness smaller than, approximately, 2 mm are used, it is preferablethat a rib is provided to the metallic cover 71 and the resin moldcompound side metallic cover 72 in order to increase the durability ofthe metallic cover 71 and the resin mold compound side metallic cover72. When such rib is provided to the metallic cover 71 and the resinmold compound side metallic cover 72 each having the thickness smallerthan approximately 2 mm, the metallic cover 71 and the resin moldcompound side metallic cover 72 will have the durability equivalent tothat of the metallic cover 71 and the resin mold compound side metalliccover 72 having the thickness of, or greater than, approximately 2 mm.

Also, the metallic cover 71 and the resin mold compound side metalliccover 72 have preferably a same shape with one another. When themetallic cover 71 and the resin mold compound side metallic cover 72have the same shape, they can be manufactured by using the same die,thereby reducing the production cost thereof. That is, pumps accordingto the present embodiment can be provided at low cost. When the metalliccover 71 and the resin mold compound side metallic cover 72 aremanufactured by using the same die, the resin mold compound sidemetallic cover 72 will have an opening for the intake portion and anopening for a drainage plug in a same manner as the metallic cover 71.In order to prevent the resin mold compound 33 from being exposedexternally through the openings and to increase the durability of theresin mold compound 33, a rib will be provided to the openings.

Third Embodiment

FIG. 4 is a diagram showing a schematic cross sectional view in theaxial direction of a pump 50 according to a third embodiment of thepresent invention. FIG. 5 is an enlarged view of a portion A shown inFIG. 4. As shown in FIG. 4, the pump 50 is a canned type pump, whereinthe pump 50 has a common structure as the pump 10 according to the firstembodiment. In FIG. 4, elements similar to those illustrated in FIG. 1are denoted by similar reference numerals, and the description of thestructure of the pump 50 is omitted.

The pump 50 according to the third embodiment comprises a stator 22including an annular shaped resin mold compound 34 having therein themolded resin 32 in which the armature 30 and the printed circuit board31 are provided. In the armature 30, the ring shaped laminated core 29and the coil 29 a are provided.

The resin mold compound 34 includes therein an annular shapedreinforcement board 5 which is formed of a metal plate. Thereinforcement board 5 is located at a molded resin portion 32 a, in theresin mold compound 34, between a cup shaped bottom portion 35 and thelower case 12. The contact between the resin mold compound 34 and thelower case 12 is similar to the contact between the resin mold compound33 and the lower case 12 according to the first embodiment.

The reinforcement board 5 which is formed of a non-magnetic material(e.g., stainless steel or aluminum alloy). The reinforcement board 5 isformed by embedding (e.g., insert molding) in the molded resin 32 whenthe resin mold compound 34 is formed by molding the stator 22 and theprinted circuit board 31. The reinforcement board 5 is located near orattached to an electronic component which is mounted on the printedcircuit board 31 and emits heat so as for the electronic component toalleviate the heat.

The reinforcement board 5 can: increase the durability of the moldedresin portion 32 a having an inferior durability compared with the restof the molded resin 32; and alleviate the pressure conducted to theresin mold compound 34 from the bottom portion 35. That is, thereinforcement board 5 prevents damages (e.g., occurrence of crack) frombeing done to the resin mold compound 34, thereby preventing the stator22 from being damaged, and prevents the resin mold compound 34 frombeing detached from the lower case 12.

Also, in order to increase the durability of the pump 50, an annularshaped reinforcement board 18 is provided by an insertion molding so asto surround a protruding portion of the intake portion 13.

Fourth Embodiment

FIG. 6 is a diagram showing a schematic cross sectional view in theaxial direction of a pump 60 according to a fourth embodiment of thepresent invention. FIG. 7 is a diagram showing an enlarged portion Bshown in FIG. 6. The pump 60 as shown in FIG. 6 is a canned type pumphaving a common structure as the pumps 10 and 50, respectively,according to the first and the third embodiments. In FIG. 6, elementssimilar to those illustrated in FIG. 4 are denoted by similar referencenumerals, and the description of the structure of the pump 60 isomitted.

The pump 60 according to the fourth embodiment comprises, similarly asthe pump 10 described above, the stator 22 and the printed circuit board31 which are molded in the molded resin 32 forming the annular shapedresin mold compound 33, wherein the stator 22 includes the ring shapedlaminated core 29 and the coil.

The resin mold compound 33 is affixed along the outer circumferentialsurface of the rotor magnet 28 of the rotor 21, and along the outercircumferential surface of the lower case 12. There is a minute gap Sbetween the inner circumferential surface of the resin mold compound 33and the outer circumferential surface of the lower case 12.

A filler 6 is provided in the gap S between the resin mold compound 33and the lower case 12 of the pump 60 according to the present embodimentof the invention. The filler 6 is provided by applying it on theinternal circumferential surface of the resin mold compound 33 and/orthe outer circumferential surface of the lower case 12 before the resinmold compound 33 is attached to the lower case 12.

The filler 6 may be an oil, a rubber or a resin substance. A silicon(e.g., rubber or resin) filler is beneficial in that, when applied onthe lower case 12, the expansion of the lower case 12 can be sustained.Also, the silicon case 12 can be easily applied and is inexpensive.

By this, the expansion of the lower case 12 due to the internal pressureof the fluid within the pump chamber 16 can be sustained, therebypreventing the occurrence of a crack at the weld line of the lower case12.

As described above, the pump according to the present inventionprovides: (1) the metallic cover 1 on the surface of the upper caseformed of the resin material; (2) the metallic cover 1 on the surface ofthe upper case 11 and on the surface of the resin mold compound 33; (3)the reinforcement board 5 in the resin mold compound 33 at the portionthereof where the resin mold compound 33 and the lower case 12 makecontact with each other; and (4) the filler 6 in the gap S between resinmold compound 33 and the lower case 12. Note, however, thataforementioned 4 elements each can be applied separately orsimultaneously.

While the invention has been described in detail, the foregoingdescription is in all aspects illustrative and not restrictive. It isunderstood that numerous other modifications and variations can bedevised without departing from the scope of the invention. Further, thepresent invention can be applied to an automatic feed water pump, anaxial pump, or to a pump commonly referred to as a reversible pump,having therein a plurality of discharge portions, in which fluid insidethe pump is directed to a predetermined discharge portion by an impellerprovided therein.

Further, the stator 22 according to the present invention is notnecessarily limited to as described above. The stator 22 can be formedby, after attaching the armature 30 to the lower case 12, filling aspace, which is generated by an exterior wall integrally formed with thelower case 12, with a potting material. The space generated by theexterior wall can be provided separately from the lower case 12 or canbe attached to the uppercase 11.

Although the forgoing description assumes that a metallic plate (e.g.,metallic cover and reinforcement board) is, in order to reinforce thedurability of the pump, provided to the upper case the lower case andthe resin mold compound, this is not limited thereto. Since an object ofthe invention is to provide an element to the upper case, the lower caseand the resin mold compound so as to increase the durability of theupper case, the lower case and the resin mold compound, the element canbe formed of a resin material having a high degree of hardness or acarbon fiber. For example, a reinforcement element for covering over theupper case, the lower case and the resin mold compound can be in anyshape if the element is able to cover over the lower case and the resinmold compound.

The pump according to the present invention can be used for a waterheater which is used for a heating system, a bath room and a kitchen.

1. A pump, comprising: a pump chamber formed, for forming therein apathway for fluid, inside a case formed of a resin material; at leastone intake portion connected to the pump chamber for intaking thereinthe fluid; at least one discharge portion connected to the pump chamberfor discharging therefrom the fluid; a rotor located inside the pumpchamber and having therein a rotor magnet, wherein the rotor rotatesalong a predetermined rotary shaft; an impeller rotating along with therotor so as to direct the fluid to a predetermined direction; a statorlocated opposing to the rotor magnet while having a gap therebetween andlocated outside of the pump chamber, wherein the stator includes thereinan armature which is a generator of a magnetic field; and a metalliccover affixed, for increasing durability of the case, to a portion ofthe case to which an internal pressure generated by the fluid inside thepump chamber is applied.
 2. The pump according to claim 1, wherein themetallic cover covers over a weld line generated on a surface of thecase, and is affixed to the case on one side and the other side of theweld line.
 3. The pump according to claim 1, wherein the internalpressure of the fluid inside the pump chamber is greater thanapproximately 250 KPa.
 4. The pump according to claim 1, wherein themetallic cover is affixed to the case by a screw at a portion of thecase radially outside of the pump chamber.
 5. The pump according toclaim 1, wherein: the case includes an upper case and a lower case in anaxial direction; the lower case is cup shaped for containing therein therotor; and the metallic cover is affixed to a top surface in an axialdirection of the upper case.
 6. The pump according to claim 1, wherein:the metallic cover is located on top side and bottom side in an axialdirection of the case; and the case is, due to the metallic coverprovided thereto, constrictedly secured in the axial direction.
 7. Thepump according to claim 1, wherein: the stator includes therein a resinmold compound having formed therein an armature molded with the resinmaterial; and the resin mold compound is located for making contact withan outer surface of the case.
 8. The pump according to claim 5, wherein:the stator includes therein a resin mold compound having formed thereinan armature molded with the resin material; and the resin mold compoundis located for making contact with at least an outer circumferentialsurface of the cup shape of the lower case.
 9. The pump according toclaim 7, wherein a resin-mold-compound-side metallic cover is affixed toan outer surface of the resin mold compound so as to cover over theouter surface of the resin mold compound.
 10. The pump according toclaim 9, wherein the case and the resin mold compound are, due to themetallic cover and the resin mold compound side cover respectivelyprovided thereto, constrictedly secured in the axial direction.
 11. Thepump according to claim 8, wherein a resin-mold-compound-side metalliccover is affixed to the outer surface of the resin mold compound so asto cover over the outer surface of the resin mold compound.
 12. The pumpaccording to claim 11, wherein the case and the resin mold compound are,due to the metallic cover and the resin mold compound side coverrespectively provided thereto, constrictedly secured in the axialdirection.
 13. The pump according to claim 10, wherein the metalliccover and the resin mold compound side metallic cover each are affixedto a pump base to which a corresponding pump is attached.
 14. The pumpaccording to claim 9, wherein a shape of the metallic cover and that ofthe resin mold compound side metallic cover are substantially identical.15. The pump according to claim 14, wherein: the metallic cover hasformed thereon an opening at an area thereof corresponding to the intakeportion; and provided is a rib for preventing an exposure, to an outsideof the pump, of the resin mold compound at an area of the opening, andfor increasing durability of the resin mold compound.
 16. A pump,comprising: a pump chamber formed inside a case, formed of a resinmaterial, for forming a pathway for fluid; at least one intake portionconnected to the pump chamber for intaking therein the fluid; at leastone discharge portion connected to the pump chamber for dischargingtherefrom the fluid; a rotor located inside the pump chamber and havingtherein a rotor magnet, the rotor rotating along a predetermined rotaryshaft; an impeller rotating along with the rotor so as to direct thefluid to a predetermined direction; and a stator located opposing to therotor magnet, while having a gap therebetween, outside of the pumpchamber, wherein the stator includes therein an armature which is agenerator of a magnetic field, wherein: the stator includes therein aresin mold compound having formed therein an armature molded with theresin material; the resin mold compound and the case make contact witheach other and are affixed to each other; and a metallic cover, forincreasing durability of the resin mold compound, is affixed to aportion of the resin mold compound.
 17. A pump, comprising: a pumpchamber formed inside a case, formed of a resin material, for forming apathway for fluid; at least one intake portion connected to the pumpchamber for intaking therein the fluid; at least one discharge portionconnected to the pump chamber for discharging therefrom the fluid; arotor located inside the pump chamber and having therein a rotor magnet,wherein the rotor rotates along a predetermined rotary shaft; animpeller rotating along with the rotor so as to direct the fluid to apredetermined direction; a stator located opposing to the rotor magnet,while having a gap therebetween, outside of the pump chamber; the statorincluding therein a resin mold compound molding therein an armaturewhich is a generator of a magnetic field; the resin mold compoundlocated such that a portion thereof makes contact with an outer surfaceof the case; and a reinforcement board embedded in the portion of theresin mold compound making contact with the case.
 18. The pump accordingto claim 14, wherein: the case includes an upper case and a lower casein an axial direction; the lower case is cup shaped for containingtherein the rotor; the resin mold compound is provided so as to coverover at least a portion of a circumferential surface and a portion of abottom surface of the cup shaped lower case; and a reinforcement boardis embedded at a bottom portion of the cup shaped lower case opposingthe rotor magnet.
 19. The pump according to claim 18, wherein: the resinmold compound has embedded therein a control circuit board below thestator; the control circuit board has a surface facing the bottomportion of the cup shaped lower case in the axial direction; and thereinforcement board is embedded between the bottom portion and thecontrol circuit board in the axial direction.
 20. The pump according toclaim 17, wherein the reinforcement board is formed of a materialselected from the group consisting of stainless steel and aluminumalloy.
 21. The pump according to claim 17, wherein: a case sidereinforcement board is embedded for increasing durability of the caseagainst an internal pressure of the fluid inside the pump chamber; andthe case side reinforcement board is provided at an area surrounding theintake portion of the case.
 22. A pump, comprising: a pump chamberformed inside a case, formed of a resin material, for forming a pathwayfor fluid; at least one intake portion connected to the pump chamber forintaking therein the fluid; at least one discharge portion connected tothe pump chamber for discharging therefrom the fluid; a rotor locatedinside the pump chamber and having therein a rotor magnet, wherein therotor rotates along a predetermined rotary shaft; an impeller rotatingalong with the rotor so as to direct the fluid to a predetermineddirection; a stator located opposing to the rotor magnet, while having agap therebetween, outside of the pump chamber, wherein the statorincludes therein an armature which is a generator of a magnetic field; ametallic cover affixed, for increasing durability of the case, to aportion of the case to which an internal pressure generated by the fluidinside the pump chamber is applied; and a case side reinforcement boardbeing embedded for increasing durability of the case against an internalpressure of the fluid inside the pump chamber, wherein the case sidereinforcement board is provided at an area surrounding the intakeportion of the case.
 23. The pump according to claim 22, wherein: thestator includes therein a resin mold compound having formed therein anarmature molded with the resin material; and the resin mold compound islocated for making contact with an outer surface of the case.
 24. Apump, comprising: a pump chamber formed inside a case, formed of a resinmaterial, for forming a pathway for fluid; at least one intake portionconnected to the pump chamber for intaking therein the fluid; at leastone discharge portion connected to the pump chamber for dischargingtherefrom the fluid; a rotor located inside the pump chamber and havingtherein a rotor magnet, wherein the rotor rotates along a predeterminedrotary shaft; an impeller rotating along with the rotor so as to directthe fluid to a predetermined direction; a stator located opposing to therotor magnet, while having a gap therebetween, outside of the pumpchamber; the stator including therein a resin mold compound moldingtherein an armature which is a generator of a magnetic field; the resinmold compound located such that a portion thereof makes contact with anouter surface of the case; and a filler provided in a space between theresin mold compound and the outer surface of the case.
 25. The pump 25according to claim 24, wherein: the case includes an upper case and alower case in an axial direction; the lower case is cup shaped forcontaining the rotor via a gap surrounding a circumferential surface anda bottom surface of the rotor magnet in the rotor; the resin moldcompound is provided so as to cover over at least a portion of acircumferential surface and a portion of a bottom surface of the cupshaped lower case; and a filler is provided at a portion of a spacebetween an outer circumferential surface and a bottom surface of the cupshaped lower case, and an inner circumferential surface of the resinmold compound.
 26. The pump according to claim 24, wherein the filler isprovided covering over a weld line generated on the case and on theresin mold compound.
 27. The pump according to claim 24, wherein thefiller is silicon based.
 28. The pump according to claim 1, wherein themetallic cover is thicker than, approximately, 2 mm.
 29. The pumpaccording to claim 1, wherein: the metallic cover is thinner than,approximately, 2 mm; and the metallic cover has provided thereon a ribso as to increase durability of the metallic cover.
 30. A pump,comprising: a pump chamber formed inside a case, formed of a resinmaterial, for forming a pathway for fluid; at least one intake portionconnected to the pump chamber for intaking therein the fluid; at leastone discharge portion connected to the pump chamber for dischargingtherefrom the fluid; a rotor located inside the pump chamber and havingtherein a rotor magnet, wherein the rotor rotates along a predeterminedrotary shaft; an impeller rotating along with the rotor so as to directthe fluid to a predetermined direction; a stator located opposing to therotor magnet, while having a gap therebetween, outside of the pumpchamber, wherein the stator includes therein an armature which is agenerator of a magnetic field; and a reinforcement element affixed, forincreasing durability of the case, to a portion of the case to which aninternal pressure generated by the fluid inside the pump chamber isapplied.
 31. The pump according to claim 30, wherein: the statorincludes therein a resin mold compound having formed therein an armaturemolded with the resin material; and the resin mold compound is locatedfor making contact with an outer surface of the case.
 32. The pumpaccording to claim 1, wherein the pump is used for a water heater usedfor a heating system operable to simultaneously distribute hot water toa plurality of outlets.